This application relates to a compressor wherein the locations of economizer injection ports are optimized.
Scroll compressors are becoming widely utilized in refrigerant compression applications. As known, a pair of scroll members have a base with a spiral wrap extending from the base. One scroll is fixed and the other orbits relative to the fixed scroll. The wraps interfit to define a plurality of compression chambers. The orbiting scroll wrap contacts the fixed scroll wrap to seal and define compression chambers. The compression chambers are moved towards a central discharge port as the orbiting scroll completes its orbiting cycle.
Refrigerant systems are also making increasing use of the economizer cycle in which a portion of the refrigerant is directed back to the compressor at an intermediate pressure between suction pressure and discharge pressure. This refrigerant is injected into the compression chambers through internal ports. This has the effect of increasing both system capacity and efficiency. In systems where the economizer cycle is optimized for maximum capacity increase, the scroll designer seeks to locate the internal ports so as to maximize the amount of injected vapor and to thus minimize the intermediate pressure.
The scroll designer has competing considerations in designing an economizer port for maximum capacity. First, the economizer port must communicate with the compression chamber at a point located as close to the main section chamber as possible but, second, must also be located such that the injected fluid cannot escape back into the main suction chamber. Such an escape of fluid would actually be detrimental to capacity. Thus, economizer ports have commonly been placed at a location such that they do not communicate with a chamber until after the orbiting scroll wrap has sealed the chamber, blocking fluid flow back to the main suction chamber.
This position, dictated by these two competing interests, results in an economizer pressure that is higher than the thermodynamic optimum for maximum capacity. This is due to the fact that the chamber pressure begins to rise as soon as the chamber is sealed off from the main suction chamber and thus the economizer port sees an elevated average pressure which is higher than the minimum pressure for maximum capacity increase. This limitation results in less than optimum capacity increase.